Synthesis and Electron Transfer Characteristics of a Neutral, Low-Band-Gap, Mixed-Valence Polyradical

Abstract

A polyradical consisting of alternating triarylamine and perchlorotriphenylmethyl radical moieties was synthesized by Horner-Emmons reaction. This compound is the first polymeric neutral mixedvalence compound that shows an intervalence charge transfer (IV-CT) band in the NIR. Comparison of the absorption spectra of the polymer with those of a reference monomer shows that the IV-CT transition is confined to one repeating unit. HOMO and LUMO levels are at -5.5 and -4.5 eV vs vacuum, respectively, as estimated by cyclic voltammetry. A very low exciton binding energy is indicated by comparison with the optical band gap (1.2 eV). The electron transfer properties of the polymer were investigated in solution by fs-pump-probe transient absorption spectroscopy. After optical excitation, the polymer shows a biexponential decay in the ps time regime. The short-living, solvent-dependent component refers to the direct decay from the IV-CT state to the ground state and the long-living, solvent-independent component is tentatively attributed to an equilibrium formation of the IV-CT state and a completely charge separated state. The charge-transport properties were investigated in films in organic field-effect transistor (OFET) devices. Electron and hole mobilities are both about 3 Â 10 -5 cm 2 V -1 s -1 , demonstrating ambipolar transport behavior of the polymer.

Organische gemischtvalente Verbindungen: ein Spielplatz für Elektronen und Löcher

“…10 À5 cm 2 V À1 s À1 . [315] Dies ist die Folge der durch die propellerfçrmigen Triarylamin-und PCTM-Gruppen hervorgerufenen amorphen Struktur. Gemischtvalente Verbindungen Angewandte Chemie peratur, obwohl keine bevorzugten intermolekularen Wechselwirkungen sichtbar sind.…”

Pyrene‐Based Dyad and Triad Leading to a Reversible Chemical and Redox Optical and Magnetic Switch

“…First, polychlorinated triphenylmethane (H-PTM) bis-phosponate and bisphosphonium bromide salt derivatives 1 and 2 were prepared from the corresponding H-PTM bis-bromomethyl derivative. [9] Coupling of those compounds under Wittig conditions with 1-pyrenecarboxaldehyde leads to a mixture of H-PTM mono and bisadducts 3 and 4 in different proportions depending on the starting compound used: bis-phosphonate 1 leads to a 1:9 proportion of 3:4 , whereas with bis-phosphonium salt 2 the ratio was found to be 1:1. Treatment of 3 and 4 with an excess of tetrabutylammonium hydroxide promotes the removal of the acidic proton at the  position to give the corresponding carbanions that were subsequently oxidized in situ using a concentrated solution of AgNO 3 in MeCN to yield the target radicals 5…”

“…H-PTM Bis-(bromethyl) and H-PTM Bis-(diethylphosphonate) derivatives were prepared according to literature procedures. [9] Synthesis of bis(bromotriphenylphosphine)- ((((perchlorophenyl)methylene)bis(2,3,5,6-tetrachloro-4,1-phenylene))bis(methylene)) salt (2). Triphenylphosphine (5.40 g, 20.60 mmol) was added to a solution of H-PTM dibromomethyl derivative (1.50g, 1.71mmol) in dry benzene (150 mL) and was heated under reflux for 20 h. The formed precipitate was filtered, washed with benzene, and dried under vacuum to yield pure compound 2 (2.17 g, 90.1 %).…”

Sulfur monochloride in organic synthesis

“…Although the yields are moderate, it is worth noting that, respectively, 13 and 30 chlorine atoms are introduced at a time into a molecule. 8,9 Scheme 2…”